Primary and secondary amines are known to form conjugates with lactose by undergoing a Maillard reaction (Maillard L. R., Comptes Rendus, 1912;154(2):66; Colaco C., Collett M., Roser B., Chem Oggi, 1996;14:32). Scheme 1 below shows the Maillard reaction of β-lactose with a primary amine. The product of this reaction is a simple glycosylamine, which is a combination of the lactose and the amine after a net loss of water. Maillard reaction products readily undergo an Amadori rearrangement to produce 1-amino-1-deoxy-2-ketoses, which exist in solution as a mixture of pyranose and furanose forms in equilibrium (see Scheme 2 below) (Wirth D., Baertschi S., Johnson R., et al., J Pharm Sci, 1998;87:31; Hodge J. E., Advances in Carbohydrate Chemistry, 1955:169–205). The seven degradants identified in formulated pregabalin were determined to be conjugates of pregabalin resulting from Maillard reactions. Heating pregabalin ((S)-3-(aminomethyl)-5-methyl hexanoic acid) (U.S. Pat. No. 6,197,819) in the presence of lactose formed significant quantities of these by-products. These compounds were isolated by preparative liquid chromatography and studied by mass spectrometry and NMR spectroscopy methods that led to the structural assignments (see Scheme 3 below). Four of these conjugates ((S)-4-isobutyl- 1-(2,3,4,5-tetrahydroxy-tetrahydro-pyran-2-ylmethyl)-pyrrolidin-2-one; (S)-4-isobutyl-1-(2,3,4,5-tetrahydroxy-tetrahydro-pyran-2-ylmethyl)-pyrrolidin-2-one; (S)-4-isobutyl-1-(2,3,4,5-tetrahydroxy-tetrahydro-pyran-2-ylmethyl)-pyrrolidin-2-one; and (S)-4-isobutyl-1-(2,3,4-trihydroxy-5-hydroxymethyl-tetrahydro-furan-2-ylmethyl)-pyrrolidin-2-one) are monoscaccarides, resulting from the Maillard reaction and Amardori rearrangement of pregabalin with either the galactose ((S)-4-isobutyl-1-(2,3,4,5-tetrahydroxy-teirahydro-pyran-2-ylmethl)-pyrrolidin-1-one and (S)-4-isobutyl-1-(2,3,4,5-tetrahydroxy-tetrahydro-pyran-2-ylmethyl)-pyrrolidin-2-one) or the glucose (S)-4-isobutyl- 1-(2,3,4,5-tetrahydroxy-tetrahydro-pyran-2-ylmethyl)-pyrrolidin-2-one; and (S)-4-isobutyl-1-(2,3,4-trihydroxy-5-hydroxymethyl-tetrahydro-furan-2-ylmethyl)-pyrrolidin-2-one) moiety of lactose. The synthesis, isolation, and spectral characterization of seven by-products are described in this application.